Roots vacuum pump

ABSTRACT

The present invention relates to a roots vacuum pump which is capable of implementing a good outer appearance and an improved layout design of a pump by forming a certain path through which a remaining compression gas is returned to a suction port side of a roots pump in a housing of a roots pump in the case that a gas compressed by a roots pump is not fully exhausted by a latter part pump and remains in an exhaust pot side of the roots pump and is capable of concurrently operating a roots pump and a latter part pump. The roots vacuum pump apparatus in which a root pump and a latter part pump are connected, includes bypass paths formed in at least one inner surface among the inner surfaces of the front cover and the rear cover for communicating the suction pot and exhaust port of the cylinder, and an one-way valve installed in an inlet of the bypass path contacting with the exhaust port for opening the bypass path when a pressure of the exhaust port exceeds a certain level.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a roots vacuum pump, and in particular to an improved roots vacuum pump which is capable of preventing a pump and motor from being damaged by an exhaust pressure by implementing a constant exhaust pressure of a roots pump for thereby significantly decreasing a working time by concurrently operating a roots pump and a latter part pump.

[0003] 2. Description of the Background Art

[0004] A roots pump apparatus is called as a mechanical booster and is used for processing a lot of gas at a short time, and an ultimate pressure is determined based on a latter part pump. The roots pump is not used lonely.

[0005] Namely, when using the roots vacuum pump apparatus(hereinafter, the roots vacuum pump apparatus represents a connection member between the roots pump and the latter part pump), as shown in FIG. 1, the roots pump and the latter part pump are connected, and the exhaust rate ratio between the latter part pump and the roots pump is 1:4-6. When the combined pumps are concurrently used, the gas sucked and discharged by the roots pump is not fully exhausted by the latter part pump due to a processing capacity difference, so that a part of compression gas remains in a portion between an exhaust port of the rots pump and a suction port of the latter part pump.

[0006] When the gas discharged from the roots pump is not fully exhausted and remains in the portion between the latter part pump and the roots pump, as the roots pump is operated, the pressure in the outlet side of the roots pump is gradually increased. Finally, the roots pump is over-loaded by a high pressure, so that the parts of the rotor of the roots pump and the motor are damaged.

[0007] In order to overcome the above problems, a certain work is processed using the latter pat pump with respect to a pressure under a vacuum degree of about 10 Torr of the vacuum facility. The above-described sequential driving method of the pump requires a long working time since the roots pump and the latter pumps are concurrently operated, and the structure of the vacuum system is complicated.

[0008] In another example, the compression gas which is not exhausted by the latter part pump and remains in a portion near of the exhaust port of the roots pump is guided to the suction port of the roots pump through a bypass return line 101 by opening a check valve 100 in order to enhance an efficiency by concurrently operating the roots pump and the latter part pump for thereby preventing an over load.

[0009] However, in the above return method of the remaining compression gas requires an external bypass return line 101 of the roots pump, an outer apparance is bad and causes an interference with another structure of the pump, so that when designing the system, a layout of the system is limited.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present invention to provide a roots vacuum pump which overcomes the problems encountered in a conventional cylinder structure.

[0011] It is another object of the present invention to provide a roots vacuum pump which is capable of implementing a good outer appearance and an improved layout design of a pump by forming a certain path through which a remaining compression gas is returned to a suction port side of a roots pump in a housing of a roots pump in the case that a gas compressed by a roots pump is not fully exhausted by a latter part pump and remains in an exhaust pot side of the roots pump and is capable of concurrently operating a roots pump and a latter part pump.

[0012] To achieve the above object, there is provided a roots vacuum pump which includes bypass paths formed in at least one inner surface among the inner surfaces of the front cover and the rear cover for communicating the suction pot and exhaust port of the cylinder, and an one-way valve installed in an inlet of the bypass path contacting with the exhaust port for opening the bypass path when a pressure of the exhaust port exceeds a certain level in the roots vacuum pump apparatus in which a suction port and an exhaust port are formed at both sides of a roots pump cylinder having a pair of rotors which are supported by a rotary shaft and are rotated in an engaged state, a front cover and motor fixing plate are sequentially engaged in one side of the cylinder, and a rear cover and a gear box are sequentially engaged in the other side of the same, and an exhaust port is connected with the latter part pump.

[0013] The one-way valve includes a valve guide installed in a wall surface of the cover opposite to the inlet of the bypass path, a valve member movable based on a guide of a valve guide for opening and closing the inlet of the bypass path an opposite direction with respect to the valve guide, an elastic member disposed between the valve member and the valve guide for generating a certain elastic force in order for the valve member to closely contact with the inlet of the bypass path, and an O-ring formed in a contact surface of the valve member.

[0014] In addition, in the present invention, a motor housing is engaged to one side of the motor fixing plate, and a can housing is engaged in such a manner that the interior of the motor housing is sealed, and a stator is installed in the interior of the can housing, and a motor rotor is fixed in an outer surface of the rotary shaft in such a manner that the motor rotor is protruded to the outside of the motor fixing plate for thereby implementing a good sealing state and an easier attaching and detaching operation of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein;

[0016]FIG. 1 is a view illustrating an example of use of a conventional roots vacuum pump;

[0017]FIG. 2 is a cross-sectional view illustrating a roots vacuum pump according to the present invention;

[0018]FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2;

[0019]FIG. 4 is a cross-sectional view taken along line B-B of FIG. 2;

[0020]FIG. 5 is a cross-sectional view taken along line C-C of FIG. 2; and

[0021]FIGS. 6 and 7 are views illustrating an operation state of a valve adapted to a roots vacuum pump according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The embodiments of the present invention will be explained with reference to the accompanying drawings.

[0023] In the drawings, reference numeral 1 represents a cylinder of a roots pump, and a suction port 11 and an exhaust port 12 are formed in the upper and lower sides of the cylinder 1, and a pair of rotors 13 are installed in the interior of the cylinder 1 and are supported by a rotary shaft 56.

[0024] As the rotors 13 are engaged each other and are rotated, a gas is sucked from a vacuum facility through the suction port 11 and is exhausted to the side of the exhaust port 12.

[0025] In a canned motor 51, a motor rotor 55 is fixed at an outer surface of the rotary shaft 56 protruded to an outer portion of a motor fixing plate 5, and a sealed can housing 53 is formed in the inner side of a motor housing 52. A stator 54 is fixed in the interior of the can housing 53, so that the canned motor 51 is easily engaged by engaging the motor housing 52 to the motor fixing plate 5.

[0026] Since the can housing 53 and the motor housing 52 are module-engaged, the motor housing 52 is engaged to the motor fixing plate 5 using a bolt for thereby completing an engagement of the motor. It is possible to easily disassembly the motor by separating the motor housing 52 from the motor fixing plate 5.

[0027] In addition, a cooling fan 58 is formed in the latter part of the motor housing 52 for preventing an over-heating of the motor, so that even when the canned motor 51 is operated for a long time, it is not over-headed and damaged. A cylindrical can 75 sealingly separates the stator 54 and the motor rotor 55 for thereby implementing a sealed state in the pump.

[0028] A rear cover 3 and a gear box 4 are sequentially installed in the other side of the cylinder 1. A gear apparatus is installed in the interior of the gear box 4 for thereby uniformly supplying a driving force to the rotors 13.

[0029] In the present invention, as a unit for preventing the gas pressure in the side of the exhaust port 12 of the cylinder 1 from being over-increased, a bypass path is formed in either a front cover 2 or the rear cover 3. In this embodiment of the present invention, first and second bypass paths 21 and 31 are formed in the front cover 2 and the rear cover 3, respectively.

[0030] The first bypass path 21 is formed in the interior of the front cover 2 for connecting the suction port 11 and the exhaust port 12, and an inlet 22 of the first bypass path 21 communicates with an outlet 12 of the cylinder 1, and the outlet 23 of the first bypass path 21 communicates with the suction port 11 of the cylinder 1.

[0031] In addition, the second bypass path 31 is formed in the interior of the rear cover 3 for connecting the suction port 11 and the exhaust port 12, and an inlet 32 of the second bypass path 21 communicates with the exhaust port 12, and the outlet 33 of the same communicates with the suction port 11 of the cylinder 1.

[0032] One-way valves 60 and 62 are formed in the inlets 22 and 32 of the bypass paths 21 and 31, and a valve guide 62 is installed in a wall surface of the front cover 2 and the rear cover 3 opposite to the inlets 22 and 32 of the first and second bypass paths 21 and 31, and an opening and closing valve member 63 which is moved along the valve guide 62 is formed in a portion opposite to the valve guide 62. An elastic member 64 is installed between the valve member 63 and the valve guide 62 for applying a certain elastic force thereto, so that the valve member 63 blocks the inlets 22 and 32 of the bypass paths 21 and 31 by an elastic force of the elastic member 64.

[0033] An O-ring 65 is installed in a sealed surface of the valve member 63, namely, in the wall surface of the inlets 22 and 32. Therefore, when the valve member 63 blocks the inlets 22 and 32, a sealing ratio is significantly increased by the O-ring 65.

[0034] A filter 71 is formed in the upper wall surface of the gear box 4 for filtering a foreign substance from the oil and gas. An outlet of the filter 71 is connected with the second bypass path 21, and a communication hole 74 is formed in the contact surface between the gear box 4 and the rear cover 3. A connection path 74 which connects the interior of the gear box 4 and the interior of the motor fixing plate 5 is formed in an inner wall surface of the cylinder 1 as shown in FIG. 3. A nozzle hole 72 having a certain size which connects the interior of the gear box 4 and the filter 71 is formed in the wall surface of the gear box 4.

[0035] When the vacuum pump apparatus is operated, the air or gas in the interiors of the motor fixing plate 5 and the gear box 4 is supplied to the filter 71 through the nozzle hole 72 based on a suction force, and the gas or gas which passes through the filter 71 is exhausted to the second bypass path 31 through the communication hole 74, so that the interiors of the gear box 4 and the motor fixing plate 5 maintain a certain vacuum state, whereby an oil lubricating various friction parts is prevented from being polluted by a foreign substance for thereby decreasing an abrasion ratio of the friction parts.

[0036] In the drawings, reference numeral 57 represents a bearing which rotatably supports the rotary shaft 56.

[0037] The operation of the present invention will be explained.

[0038] When a power is supplied to a root vacuum pump apparatus, and the canned motor 51 is driven, the rotor 13 is rotated, and the gas is sucked from the vacuum facility through the suction port 11 and is exhausted to the side of the exhaust port 12. The gas exhausted to the exhaust port 12 is sucked by a latter part pump(not shown) and compressed and exhausted to the outside.

[0039] At this time, at an initial operation stage of the apparatus, the gas exhausted to the exhaust port 12 is not fully supplied to the latter part pump side due to a large processing capacity difference between the roots pump and the latter part pump, but remains between the exhaust port 12 and the latter part pump.

[0040] As the gas is gradually gathered in the exhaust port 12, the gas pressure is increased. At the time when the pressure of the gas exceeds the elastic force of the elastic member 64 which elastically supports the valve member 63, the valve member 63 compresses the elastic member 64 and moves for thereby opening the inlets 22 and 32 of the first and second bypass paths 21 and 31.

[0041] As shown in FIG. 7, the inlets 22 and 32 are opened, the gas in the exhaust port 12 is bypassed to the suction port 11 of the cylinder 1 through the bypass paths 21 and 31 and is recirculated for thereby decreasing the gas pressure in the side of the exhaust port 12.

[0042] When the gas pressure in the side of the exhaust port 12 is decreased, the valve member 63 is forwardly moved by an elastic force of the elastic member 64 for thereby blocking the inlets 21 and 31 of the first and second bypass paths 21 and 31 as shown in FIG. 6.

[0043] When the valve member 63 blocks the inlets 21 and 31, since the O-ring 65 closely contacts with the inlets 21 and 31 for thereby implementing a good sealing state.

[0044] As the gas is gathered in the side of the exhaust port 12, whenever the gas pressure is increased, the valve member 63 is opened, and the gas is recirculated in the direction of the suction port 11. Therefore, the gas pressure in the side of the exhaust port 12 of the cylinder 1 maintains a certain pressure for thereby preventing a certain damage of the pump and motor. In addition, since the roots vacuum pump and latter part pump are concurrently operated, it is possible to decrease the working time.

[0045] In addition, since the bypass paths are formed in the interiors of the front cover and rear cover, respectively, an outer appearance of the roots vacuum pump is good, and the size of the pump is decreased.

[0046] As described above, in the present invention, the bypass paths are formed in the interiors of the front cover and the rear cover for connecting the suction port side and the exhaust port side of the roots pump cylinder. An one-way valve which is automatically opened and closed when an exhaust pressure in the side of the exhaust of the cylinder exceeds a certain reference value is formed in the inlet of the bypass path, so that it is possible to prevent a certain dampage of the pump apparatus and the motor due to the over load by bypassing the remaining compression gas which is not processed by the latter part pump to the side of the roots pump suction port. In addition, in the present invention, since the roots pump and the latter pat pump which have a large capacity difference are concurrently processed, it is possible to significantly decrease the working time, and since the bypass paths are formed in the pump housing, not in the outside of the system, an outer appearance looks good, and the layout of the design is not limited.

[0047] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. 

What is claimed is:
 1. In a roots vacuum pump apparatus in which a suction port and an exhaust port are formed at both sides of a roots pump cylinder having a pair of rotors which are supported by a rotary shaft and are rotated in an engaged state, a front cover and motor fixing plate are sequentially engaged in one side of the cylinder, and a rear cover and a gear box are sequentially engaged in the other side of the same, and an exhaust port is connected with the latter part pump, a roots vacuum pump apparatus, comprising: bypass paths formed in at least one inner surface among the inner surfaces of the front cover and the rear cover for communicating the suction pot and exhaust port of the cylinder; and an one-way valve installed in an inlet of the bypass path contacting with the exhaust port for opening the bypass path when a pressure of the exhaust port exceeds a certain level.
 2. The apparatus of claim 1, wherein said one-way valve includes a valve guide installed in a wall surface of the cover opposite to the inlet of the bypass path, a valve member movable based on a guide of a valve guide for opening and closing the inlet of the bypass path an opposite direction with respect to the valve guide, an elastic member disposed between the valve member and the valve guide for generating a certain elastic force in order for the valve member to closely contact with the inlet of the bypass path, and an 0-ring formed in a contact surface of the valve member.
 3. The apparatus of claim 1, wherein a motor housing is engaged to one side of the motor fixing plate, and a can housing is engaged in such a manner that the interior of the motor housing is sealed, and a stator is installed in the interior of the can housing, and a motor rotor is fixed in an outer surface of the rotary shaft in such a manner that the motor rotor is protruded to the outside of the motor fixing plate for thereby implementing a good sealing state and an easier attaching and detaching operation of the motor. 